Assessing the capacity of biochar to stabilize copper and lead in contaminated sediments using chemical and extraction methods

Because of its high adsorption capacity, biochar has been used to stabilize heavy metals when remediating contaminated soils; to date, however, it has seldom been used to remediate contaminated sediment. In this study, a biochar was used as a stabilization agent to remediate Cu-and Pb-contaminated sediments, collected from three locations in or close to Beijing. The sediments were mixed with a palm sawdust gasified biochar at a range of weight ratios (2.5%, 5%, and 10%) and incubated for 10, 30, or 60 days. The performance of the different treatments and the heavy metal fractions in the sediments were assessed using four extraction methods, including diffusive gradients in thin films, the porewater concentration, a sequential extraction, and the toxicity characteristic leaching procedure. The results showed that biochar could enhance the stability of heavy metals in contaminated sediments. The degree of stability increased as both the dose of biochar and the incubation time increased. The sediment pH and the morphology of the metal crystals adsorbed onto the biochar changed as the contact time increased. Our results showed that adsorption, metal crystallization, and the pH were the main controls on the stabilization of metals in contaminated sediment by biochar

Roles of Phosphorus Sources in Microbial Community Assembly for the Removal of Organic Matters and Ammonia in Activated Sludge

Various phosphorus sources are utilized by microbes in WWTPs, eventually affecting microbial assembly and functions. This study identified the effects of phosphorus source on microbial communities and functions in the activated sludge. By cultivation with 59 phosphorus sources, including inorganic phosphates (IP), nucleoside-monophosphates (NMP), cyclic-nucleoside-monophosphates (cNMP), and other organophosphates (OP), we evaluated the change in removal efficiencies of total organic carbon (TOC) and ammonia, microbial biomass, alkaline phosphatase (AKP) activity, microbial community structure, and AKP-associated genes. TOC and ammonia removal efficiency was highest in IP (64.8%) and cNMP (52.3%) treatments. Microbial community structure changed significantly across phosphorus sources that IP and cNMP encouraged Enterobacter and Aeromonas, respectively. The abundance of phoA and phoU genes was higher in IP treatments, whereas phoD and phoX genes dominated OP treatments. Our findings suggested that the performance of WWTPs was dependent on phosphorus sources and provided new insights into effective WWTP management

New naphthalene whole-cell bioreporter for measuring and assessing naphthalene in polycyclic aromatic hydrocarbons contaminated site

A new naphthalene bioreporter was designed and constructed in this work. A new vector, pWH1274_Nah, was constructed by the Gibson isothermal assembly fused with a 9 kb naphthalene-degrading gene nahAD (nahAa nahAb nahAc nahAd nahB nahF nahC nahQ nahE nahD) and cloned into Acinetobacter ADPWH_lux as the host, capable of responding to salicylate (the central metabolite of naphthalene). The ADPWH_Nah bioreporter could effectively metabolize naphthalene and evaluate the naphthalene in natural water and soil samples. This whole-cell bioreporter did not respond to other polycyclic aromatic hydrocarbons (PAHs; pyrene, anthracene, and phenanthrene) and demonstrated a positive response in the presence of 0.01 μM naphthalene, showing high specificity and sensitivity. The bioluminescent response was quantitatively measured after a 4 h exposure to naphthalene, and the model simulation further proved the naphthalene metabolism dynamics and the salicylate-activation mechanisms. The ADPWH_Nah bioreporter also achieved a rapid evaluation of the naphthalene in the PAH-contaminated site after chemical spill accidents, showing high consistency with chemical analysis. The engineered Acinetobacter variant had significant advantages in rapid naphthalene detection in the laboratory and potential in situ detection. The state-of-the-art concept of cloning PAHs-degrading pathway in salicylate bioreporter hosts led to the construction and assembly of high-throughput PAH bioreporter array, capable of crude oil contamination assessment and risk management

Is China's fifth-largest inland lake to dry-up? Incorporated hydrological and satellite-based methods for forecasting Hulun Lake water levels

Hulun Lake, China’s fifth-largest inland lake, experienced severe declines in water level in the period of 2000-2010. This has prompted concerns whether the lake is drying up gradually. A multi-million US dollar engineering project to construct a water channel to transfer part of the river flow from a nearby river to maintain the water level was completed in August 2010. This study aimed to advance the understanding of the key processes controlling the lake water level variation over the last five decades, as well as investigate the impact of the river transfer engineering project on the water level. A water balance model was developed to investigate the lake water level variations over the last five decades, using hydrological and climatic data as well as satellite-based measurements and results from land surface modelling. The investigation reveals that the severe reduction of river discharge (-364±64 mm/yr, ~70% of the five-decade average) into the lake was the key factor behind the decline of the lake water level between 2000 and 2010. The decline of river discharge was due to the reduction of total runoff from the lake watershed. This was a result of the reduction of soil moisture due to the decrease of precipitation (-49±45 mm/yr) over this period. The water budget calculation suggests that the groundwater component from the surrounding lake area as well as surface run off from the un-gauged area surrounding the lake contributed ~ net 210 Mm3/yr (equivalent to ~ 100 mm/yr) water inflows into the lake. The results also show that the water diversion project did prevent a further water level decline of over 0.5 m by the end of 2012. Overall, the monthly water balance model gave an excellent prediction of the lake water level fluctuation over the last five decades and can be a useful tool to manage lake water resources in the future

Separating and characterizing functional alkane degraders from crude-oil-contaminated sites via magnetic nanoparticle-mediated isolation

Uncultivable microorganisms account for over 99% of all species on the planet, but their functions are yet not well characterized. Though many cultivable degraders for n-alkanes have been intensively investigated, the roles of functional n-alkane degraders remain hidden in the natural environment. This study introduces the novel magnetic nanoparticle-mediated isolation (MMI) technology in Nigerian soils and successfully separates functional microbes belonging to the families Oxalobacteraceae and Moraxellaceae, which were dominant and responsible for alkane metabolism in situ. The alkR-type n-alkane monooxygenase genes, instead of alkA- or alkP-type, were the key functional genes involved in the n-alkane degradation process. Further physiological investigation via a BIOLOG PM plate revealed some carbon (Tween 20, Tween 40 and Tween 80) and nitrogen (tyramine, L-glutamine and D-aspartic acid) sources promoting microbial respiration and n-alkane degradation. With further addition of promoter carbon or nitrogen sources, the separated functional alkane degraders significantly improved n-alkane biodegradation rates. This suggests that MMI is a promising technology for separating functional microbes from complex microbiota, with deeper insight into their ecological functions and influencing factors. The technique also broadens the application of the BIOLOG PM plate for physiological research on functional yet uncultivable microorganisms

Response of soil bacterial community composition and its associated geochemical parameters to rapid short-term cyclic groundwater-level oscillations: soil column experiments

Groundwater-level oscillations change geochemical conditions, carbon cycling processes and bacterial community composition, and these changes may vary vertically with depth in a soil. In this study, soil column experiments were conducted to explore variations in soil bacterial community composition and its associated geochemical parameters to rapid short-term cyclic groundwater-level oscillations driven by natural fluctuations (NF) and rainfall infiltration (RI) and the results are compared with quasi static (QS) column. Water saturation patterns in vadose and oscillated zones, and oxygen level patterns, soil total organic carbon (TOC) removal rates and soil bacterial community composition in vadose, oscillated and saturated zones were evaluated. Results showed that water saturation and oxygen level oscillated with groundwater level in NF and RI columns. TOC removal rates in RI column were the highest across vadose (~38.4%), oscillated (~35.8%) and saturated (~35.2%) zones. Deltaproteobacteria, which was significantly correlated with TOC removal (p < 0.05), exhibited relatively higher abundances in the vadose and oscillated zones of RI column than those of QS and NF columns. Soil bacterial community structure was dynamic at the class level due to water saturation, oxygen level and TOC removal. TOC removal was the driver to separate distribution of bacterial community structure in the vadose and oscillated zones of RI column from those of QS and NF columns. This study suggests that RI induced rapid short-term cyclic groundwater-level oscillations could significantly influence both soil carbon cycle and bacterial community structure in vadose and oscillated zones

Ensuring water resource security in China; the need for advances in evidence based policy to support sustainable management.

China currently faces a water resource sustainability problem which is likely to worsen into the future. The Chinese government is attempting to address this problem through legislative action, but faces severe challenges in delivering its high ambitions. The key challenges revolve around the need to balance water availability with the need to feed a growing population under a changing climate and its ambitions for increased economic development. This is further complicated by the complex and multi-layered government departments, often with overlapping jurisdictions, which are not always aligned in their policy implementation and delivery mechanisms. There remain opportunities for China to make further progress and this paper reports on the outcomes of a science-to-policy roundtable meeting involving scientists and policy-makers in China. It identifies, in an holistic manner, new opportunities for additional considerations for policy implementation, continued and new research requirements to ensure evidence-based policies are designed and implemented and identifies the needs and opportunities to effectively monitor their effectiveness. Other countries around the world can benefit from assessing this case study in China

Response of Microbial Community Stability to Chemical Oxidation Remediation Process in a Petroleum Hydrocarbon Contaminated Groundwater Site

The stability of the microbial community is a vital indicator of microbial ecosystems. However, the mechanism of microbial community stability during in situ chemical oxidation in petroleum-hydrocarbon-polluted groundwater is unclear. This study analyzed the biomass, diversity, co-occurrence network feature and negative cohesion of microbial community at different stages to identify the changes in microbial community stability under chemical oxidation. In addition, microbial module compositions and crucial functions were analyzed to further explore the reason for the change in community stability at the module level. Multiple regression analysis was conducted to explore the microbial module explanatory degree to microbial community stability changes. The results indicated that the microbial community stability was destroyed by chemical oxidation. The carbon source effect was the main reason in the early oxidation stage, while the oxidation stress effect was the main reason in the late oxidation stage. Most microbial modules were transformed from K-strategists to r-strategists, and modular keystones were transformed to stress-tolerant species in the oxidation stage. This study suggested that microbial clusters were essential indicators of the microbial community in petroleum hydrocarbon groundwater during the chemical oxidation period